The present invention relates to a method and a device for optically measuring a distance.
EP 1 152 259 A2 discloses an optical distance sensor, which permits determining the distance between the optical distance sensor and a target object. Optical distance sensors of this type are used, for example, in industrial quality controls or manufacturing processes, where metal sheet thicknesses or distances of semiconductor plates from a tool are to be detected. Furthermore, optical distance sensors are used for positioning objects, for example, in the case of elevator installations, where the elevator car is to be positioned in each floor in a desired position. Likewise in storage systems it is necessary to position the access systems in an accordingly accurate manner for accessing stored goods.
For determining the phase shift between emitted and received light beams, the optical distance sensor as disclosed in EP 1 152 259 A2 uses in its distance evaluation circuit a synchronous rectifier, which supplies a voltage proportionate to the phase difference. The voltage as output by the synchronous rectifier is used to regulate a final control element, so that the voltage reaches a predetermined value.
A thus-realized regulation is a continuous regulation that requires a large amount of circuitry. To obtain an adequately accurate and rapid regulating loop, it becomes moreover necessary to further increase the required circuitry.
It is therefore an object of the present invention to provide and further develop a method for optically measuring a distance, wherein the required circuitry for the distance evaluation circuit may be reduced, while maintaining a high accuracy, and wherein the regulating speed can be further increased.